Method of manufacturing a semiconductor device having a contact plug

ABSTRACT

There is provided a semiconductor device that includes: a transistor having a gate electrode, a source region, and a drain region; a first inter-layer insulation film covering the transistor; a first contact plug formed penetrating through the first inter-layer insulation film and connected to either the source region or the drain region; a second inter-layer insulation film covering the first contact plug; a groove extending in the second inter-layer insulation film in a same direction as an extending direction of the gate electrode and exposing a top surface of the first contact plug at a bottom thereof; a second contact plug connected to the first contact plug and formed in the groove; and a wiring pattern extending on the second inter-layer insulation film so as to traverse the groove and integrated with the second contact plug.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending application Ser. No.12/545,433 filed Aug. 21, 2009, which claims foreign priority toJapanese patent application 2008-21373 filed Aug. 22, 2008. The entirecontent of each of these applications is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and amanufacturing method thereof, and, particularly to a semiconductordevice in which a plurality of contact plugs are closely formed and amanufacturing method thereof.

2. Description of Related Art

A number of transistors in a semiconductor device are formed on asilicon substrate. Source regions and drain regions of the transistorsare connected to wiring patterns or various elements formed on upperlayers via various contact electrodes. For example, either the sourceregion or the drain region of a cell transistor are connected to bitline via a cell contact plug and a bit contact plug in a DRAM (DynamicRandom Access Memory), which is a typical semiconductor device (seeJapanese Patent Application Laid-open No. 2008-72132).

FIGS. 26 to 31 are process diagrams for explaining a general method ofconnecting either the source regions or the drain regions in a DRAM tobit lines. FIGS. 26A, 28A, and 30A are schematic plan views in eachprocess, FIGS. 26B, 28B, and 30B are schematic cross-sectional viewstaken along a line X-X in each of the plan views, FIGS. 27A, 29A, and31A are schematic cross-sectional views taken along a line Y-Y in eachof the plan views, and FIGS. 27B, 29B, and 31B are schematiccross-sectional views taken along a line Z-Z in each of the plan views.

As shown in FIGS. 26A, 26B, 27A and 27B, a plurality of transistors areformed by forming a plurality of gate electrodes 31, and a plurality ofsource regions and drain regions 32 on a semiconductor substrate 300.After forming a cap insulation film 33 composed of a silicon nitridefilm covering the side and top surfaces of each gate electrode 31, afirst inter-layer insulation film 34 covering the plurality oftransistors is formed. Cell contact plugs 35 connected to either thesource regions or the drain regions 32 are formed in the inter-layerinsulation film 34, and a second inter-layer insulation film 36 isformed thereon. Subsequently, a plurality of contact holes 37 exposingthe top surfaces of the cell contact plugs 35 are formed in theinter-layer insulation film 36. As shown in FIGS. 28A, 28B, 29A and 29B,an conductive material filling the plurality of contact holes 37 isformed, which is flattened by CMP (Chemical Mechanical Polishing) toform a plurality of bit contact plugs 38. By patterning the conductivematerial, subsequent to formation thereof on the bit contact plugs 38, aplurality of bit lines 39 are formed, each of which connecting to eachbit contact plug 38, as shown in FIGS. 30A, 30B, 31A and 31B.

With a manufacturing method shown in FIGS. 26A to 31B, there has been apossibility of short-circuiting between adjacent contact plugs 38 as thearray pitch of the bit contact plugs 38 (contact holes 37) become verynarrow due to progress of high integration. Therefore, there has been aproblem that a very high precision is required for lithography andpatterning (etching) to form the contact holes 37.

While conventional problems related to the present invention have beenexplained above by exemplifying a memory cell of a DRAM, these problemscan similarly occur to other semiconductor devices.

SUMMARY

The present invention seeks to solve one or more of the above problems,or to improve upon those problems at least in part.

In one embodiment, there is provided a semiconductor device thatincludes: a transistor having a gate electrode, a source region, and adrain region; a first inter-layer insulation film covering thetransistor; a first contact plug formed penetrating through the firstinter-layer insulation film and connected to either the source region orthe drain region; a second inter-layer insulation film covering thefirst contact plug; a groove extending in the second inter-layerinsulation film in a same direction as an extending direction of thegate electrode and exposing a top surface of the first contact plug at abottom thereof; a second contact plug connected to the first contactplug and formed in the groove; and a wiring pattern extending on thesecond inter-layer insulation film so as to traverse the groove andintegrated with the second contact plug.

In one embodiment, there is provided a manufacturing method of asemiconductor device that includes: forming a transistor having a gateelectrode, a source region, and a drain region; forming a firstinter-layer insulation film covering the transistor; forming a firstcontact plug penetrating through the first inter-layer insulation filmand connected to either the source region or the drain region; forming asecond inter-layer insulation film covering the first contact plug;forming a groove extending in the second inter-layer insulation film ina same direction as an extending direction of the gate electrode andexposing a top surface of the first contact plug at a bottom thereof;forming an conductive material in the groove and on the secondinter-layer insulation film; and patterning the conductive material onthe second inter-layer insulation film and the conductive material inthe groove using a mask to form a second contact plug connected to thefirst contact plug and a wiring pattern extending on the secondinter-layer insulation film so as to traverse the groove, the wiringpattern being integrated with the second contact plug.

According to the present invention, the groove extending in the samedirection as that of the extending gate electrodes and exposing the topsurface of the first contact plugs at the bottom is formed on the secondinter-layer insulation film, and the second contact plugs connected tothe first contact plugs are formed in the groove. That is, the secondcontact plugs can be formed by patterning the conductive material afterthe conductive material is formed in the groove. Therefore, lithographyand patterning (etching) can be easily performed even if the array pitchof the second contact plugs is narrow, because the formation of minutecontact holes is not required when forming the second contact plugs.

Furthermore, because the second contact plugs and the wiring patternsintegrated with the second contact plugs can be formed by forming theconductive material in the groove and on the second inter-layerinsulation film and patterning the same, the formation of the conductivematerial or CMP in order to form the second contact plugs can beeliminated and simplifying the manufacturing process thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be moreapparent from the following description of certain preferred embodimentstaken in conjunction with the accompanying drawings, in which:

FIGS. 1A and 1B show the structure of a semiconductor device 100according to a first embodiment of the invention, where FIG. 1A is aschematic plan view, FIG. 1B is a schematic cross-sectional view along aline A-A in FIG. 1A,

FIGS. 2A and 2B show the structure of the semiconductor device 100according to the first embodiment of the invention, where FIG. 2A is aschematic cross-sectional view along a line B-B in FIG. 1A, and FIG. 2Bis a schematic cross-sectional view along a line C-C in FIG. 1A;

FIGS. 3A and 3B show a manufacturing process of the semiconductor device100 (forming of a first contact plug), where FIG. 3A is a schematic planview, and FIG. 3B is a schematic cross-sectional view taken along a lineA-A in FIG. 3A;

FIGS. 4A and 4B show the manufacturing process of the semiconductordevice 100 (forming of the first contact plug 15), where FIG. 4A is across-sectional view taken along a line B-B in FIG. 3A, and FIG. 4B is aschematic cross-sectional view taken along a line C-C in FIG. 3A;

FIGS. 5A and 5B show a manufacturing process of the semiconductor device100 (forming of a resist mask 19), where FIG. 5A is a schematic planview, and FIG. 5B is a schematic cross-sectional view taken along a lineA-A in FIG. 5A;

FIGS. 6A and 6B show the manufacturing process of the semiconductordevice 100 (forming of the resist mask 19), where FIG. 6A is across-sectional view taken along a line B-B in FIG. 5A, and FIG. 6B is aschematic cross-sectional view taken along a line C-C in FIG. 5A;

FIGS. 7A and 7B show a manufacturing process of the semiconductor device100 (forming of a groove 17), where FIG. 7A is a schematic plan view,and FIG. 7B is a schematic cross-sectional view taken along a line A-Ain FIG. 7A;

FIGS. 8A and 8B show the manufacturing process of the semiconductordevice 100 (forming of the groove 17), where FIG. 8A is across-sectional view taken along a line B-B in FIG. 7A, and FIG. 8B is aschematic cross-sectional view taken along a line C-C in FIG. 7A;

FIGS. 9A and 9B show a manufacturing process of the semiconductor device100 (forming of an conductive material 18), where FIG. 9A is a schematicplan view, and FIG. 9B is a schematic cross-sectional view taken along aline A-A in FIG. 9A;

FIGS. 10A and 10B show the manufacturing process of the semiconductordevice 100 (forming of the conductive material 18), where FIG. 10A is across-sectional view taken along a line B-B in FIG. 9A, and FIG. 10B isa schematic cross-sectional view taken along a line C-C in FIG. 9A;

FIGS. 11A and 11B show a manufacturing process of the semiconductordevice 100 (forming of a mask layer 20), where FIG. 11A is a schematicplan view, and FIG. 11B is a schematic cross-sectional view taken alonga line A-A in FIG. 11A;

FIGS. 12A and 12B show the manufacturing process of the semiconductordevice 100 (forming of the mask layer 20), where FIG. 12A is across-sectional view taken along a line B-B in FIG. 11A, and FIG. 12B isa schematic cross-sectional view taken along a line C-C in FIG. 11A;

FIGS. 13A and 13B show a manufacturing process of the semiconductordevice 100 (forming of wiring patterns 18 w and second contact plugs 18c), where FIG. 13A is a schematic plan view, and FIG. 13B is a schematiccross-sectional view taken along a line A-A in FIG. 13A;

FIGS. 14A and 14B show the manufacturing process of the semiconductordevice 100 (forming of the wiring patterns 18w and the second contactplugs 18 c), where FIG. 14A is a cross-sectional view taken along a lineB-B in FIG. 13A, and FIG. 14B is a schematic cross-sectional view takenalong a line C-C in FIG. 13A;

FIG. 15 is a schematic cross-sectional view for explaining a problem inthe first embodiment;

FIGS. 16A and 16B show the structure of a semiconductor device 200according to a second embodiment of the invention, where FIG. 16A is aschematic plan view, FIG. 16B is a schematic cross-sectional view alonga line D-D in FIG. 16A,

FIGS. 17A and 17B show the structure of the semiconductor device 200according to the first embodiment of the invention, where FIG. 17A is aschematic cross-sectional view along a line E-E in FIG. 16A, and FIG.17B is a schematic cross-sectional view along a line F-F in FIG. 16A;

FIGS. 18A and 18B show a manufacturing process of the semiconductordevice 200 (forming of a resist mask 29), where FIG. 18A is a schematicplan view, and FIG. 18B is a schematic cross-sectional view taken alonga line D-D in FIG. 18A;

FIGS. 19A and 19B show the manufacturing process of the semiconductordevice 200 (forming of the resist mask 29), where FIG. 19A is across-sectional view taken along a line E-E in FIG. 18A, and FIG. 19B isa schematic cross-sectional view taken along a line F-F in FIG. 18A;

FIGS. 20A and 20B show a manufacturing process of the semiconductordevice 200 (forming of a groove 27), where FIG. 20A is a schematic planview, and FIG. 20B is a schematic cross-sectional view taken along aline D-D in FIG. 20A;

FIGS. 21A and 21B show the manufacturing process of the semiconductordevice 200 (forming of the groove 27), where FIG. 21A is across-sectional view taken along a line E-E in FIG. 20A, and FIG. 21B isa schematic cross-sectional view taken along a line F-F in FIG. 20A;

FIGS. 22A and 22B show a manufacturing process of the semiconductordevice 200 (forming of an conductive material 28 and a mask layer 30),where FIG. 22A is a schematic plan view, and FIG. 22B is a schematiccross-sectional view taken along a line D-D in FIG. 22A;

FIGS. 23A and 23B show the manufacturing process of the semiconductordevice 200 (forming of the conductive material 28 and the mask layer30), where FIG. 23A is a cross-sectional view taken along a line E-E inFIG. 22A, and FIG. 23B is a schematic cross-sectional view taken along aline F-F in FIG. 22A;

FIGS. 24A and 24B show a manufacturing process of the semiconductordevice 200 (forming of wiring patterns 28 w and second contact plugs 28c), where FIG. 24A is a schematic plan view, and FIG. 24B is a schematiccross-sectional view taken along a line D-D in FIG. 24A;

FIGS. 25A and 25B show the manufacturing process of the semiconductordevice 200 (forming of the wiring patterns 28 w and the second contactplugs 28 c), where FIG. 25A is a cross-sectional view taken along a lineE-E in FIG. 24A, and FIG. 25B is a schematic cross-sectional view takenalong a line F-F in FIG. 24A;

FIGS. 26A and 26B show a manufacturing process (forming of contact holes37) for explaining a general method of connecting either the sourceregions or the drain regions to bit lines in a DRAM, where FIG. 26A is aschematic plan view, and FIG. 26B is a schematic cross-sectional viewtaken along a line X-X in FIG. 26A;

FIGS. 27A and 27B show the manufacturing process (forming of contactholes 37) for explaining the general method of connecting either thesource regions or the drain regions to bit lines in a DRAM, where FIG.27A is a cross-sectional view taken along a line Y-Y in FIG. 26A, andFIG. 27B is a schematic cross-sectional view taken along a line Z-Z inFIG. 26A;

FIGS. 28A and 28B show a manufacturing process (forming of bit contactplugs 38) for explaining a general method of connecting either thesource regions or the drain regions to bit lines in a DRAM, where FIG.28A is a schematic plan view, and FIG. 28B is a schematiccross-sectional view taken along a line X-X in FIG. 28A;

FIGS. 29A and 29B show the manufacturing process (forming of the bitcontact plugs 38) for explaining the general method of connecting eitherthe source regions or the drain regions to bit lines in a DRAM, whereFIG. 29A is a cross-sectional view taken along a line Y-Y in FIG. 28A,and FIG. 29B is a schematic cross-sectional view taken along a line Z-Zin FIG. 28A;

FIGS. 30A and 30B show a manufacturing process (forming of bit lines 39)for explaining a general method of connecting either the source regionsor the drain regions to bit lines in a DRAM, where FIG. 30A is aschematic plan view, and FIG. 30B is a schematic cross-sectional viewtaken along a line X-X in FIG. 30A; and

FIGS. 31A and 31B show the manufacturing process (forming of the bitlines 39) for explaining the general method of connecting either thesource regions or the drain regions to bit lines in a DRAM, where FIG.31A is a cross-sectional view taken along a line Y-Y in FIG. 30A, andFIG. 31B is a schematic cross-sectional view taken along a line Z-Z inFIG. 30A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will be explained belowin detail with reference to the accompanying drawings.

First Embodiment

The semiconductor device 100 according to the first embodiment is aDRAM, with FIGS. 1A, 1B, 2A and 2B showing the structure when theformation of its bit lines 18 w is completed.

As shown in FIGS. 1A, 1B, 2A and 2B, the semiconductor device 100according to the first embodiment includes a plurality of transistorseach having a gate electrode 11 and a source region and a drain region12 formed on a semiconductor substrate 10; first contact plugs (cellcontact plugs) 15 connected to either the source regions or the drainregions 12, respectively; second contact plugs (bit contact plugs) 18 cconnected to the first contact plugs 15, respectively; and wiringpatterns 18 w connected to the second contact plugs 18 c, respectively.

The side and top surfaces of each gate electrode 11 are covered with asilicon nitride film working as a cap insulation film 13. A silicondioxide film working as a first inter-layer insulation film 14 is formedso as to cover the entire semiconductor substrate 10 including the capinsulation film 13. It is preferred that the thickness of the firstinter-layer insulation film 14 is about 200 to 300 nm. The first contactplugs 15 are connected to either the source regions or the drain region12, penetrating through the first inter-layer insulation film 14,respectively. A silicon dioxide film is formed on the first inter-layerinsulation film 14 to work as a second inter-layer insulation film 16. Agroove 17 linearly extending in the same direction as the extendingdirection of the gate electrodes 11 and exposing the top surface of thefirst contact plugs 15 at the bottom is formed on the second inter-layerinsulation film 16. In the groove 17, a plurality of second contactplugs 18 c are arranged spaced apart from each other with apredetermined interval. Wiring patterns 18 w extend on the secondinter-layer insulation film 16 so as to traverse the groove 17, and areintegrated with the second contact plugs 18 c.

The first contact plugs 15, the second contact plugs 18 c, and thewiring patterns 18 w are formed by a conductive material, where W orW/WN film can be used, for example.

The manufacturing method of the semiconductor device 100 according tothe first embodiment is explained below.

FIGS. 3A to 14B are process diagrams for explaining the manufacturingmethod of the semiconductor device 100 according to the firstembodiment, where FIGS. 3A, 5A, 7A, 9A, 11A, and 13A are schematic planviews in each process, FIGS. 3B, 5B, 7B, 9B, 11B, and 13B are schematiccross-sectional views taken along a line A-A in each of the plan views,FIGS. 4A, 6A, 8A, 10A, 12A, and 14A are schematic cross-sectional viewstaken along a line B-B in each of the plan views, and FIGS. 4B, 6B, 8B,10B, 12B, and 14B are schematic cross-sectional views taken along a lineC-C in each of the plan views.

First, as shown in FIGS. 3A, 3B, 4A and 4B, the transistors are formedby forming the gate electrodes 11, and forming the source regions anddrain regions 12 on the semiconductor substrate 10. After forming thecap insulation film 13 composed of the silicon nitride film covering theside and top surfaces of respective gate electrodes 11, the firstinter-layer insulation film 14 covering the transistors is formed. Thefirst contact plugs (cell contact plugs) 15 connected to either thesource regions or drain regions 12 are formed on the inter-layerinsulation film 14.

As shown in FIGS. 5A, 5B, 6A and 6B, the second inter-layer insulationfilm 16 is formed on the first inter-layer insulation film 14.Subsequently, the resist mask 19 is formed on the second inter-layer 16.The resist mask 19 is formed so as to have a groove-like opening 19oplocated over the cell contact plugs 15.

Subsequently, by patterning the second inter-layer insulation film 16using the resist mask 19, the groove 17 linearly extending in the samedirection as an extending direction of the gate electrodes 11 andexposing the top surface of the first contact plugs 15 at a bottomthereof is formed on the second inter-layer insulation film 16, as shownin FIGS. 7A, 7B, 8A and 8B.

As shown in FIGS. 9A, 9B, 10A and 10B, a conductive material 18 is thenformed in the groove 17 and on the second inter-layer insulation film16. Subsequently, as shown in FIGS. 11A, 11B, 12A and 12B, a mask layer20 having plural patterns across the groove 17 is formed. It ispreferable to use a silicon nitride film working as the material of themask layer 20.

By patterning the conductive material 18 in the groove 17, as well aspatterning the conductive material 18 on the second inter-layerinsulation film 16, using the mask layer 20, wiring patterns (bit lines)18 w that are patterned across the groove 17 and the second contactplugs (bit contact plugs) 18 c are simultaneously formed as shown inFIGS. 13A, 13B, 14A and 14B. According to the manner described above,the bit lines 18 w and the bit contact plugs 18 c are integrally formed.

The structure shown in FIGS. 1A, 1B, 2A and 2B can be subsequentlyobtained by removing the mask layer 20.

According to the first embodiment, it is possible to simultaneouslyfabricate the bit lines while forming the bit contact plugs 18c.Therefore, formation and etching of mask layer only for the bit contactplugs 18 c can be eliminated and simplifying the process thereby,compared with forming the bit contact plugs 18 c and the bit linesindividually.

Additionally, high-precision lithography and etching can be eliminatedby forming the groove 17 and patterning the conductive material 18embedded in the groove 17 as a method of forming the bit contact plugs18 c, instead of forming a contact hole and embedding the conductivematerial therein.

In the first embodiment, however, there are cases that the followingproblem arises, which are explained with reference to FIG. 15. FIG. 15corresponds to the schematic cross-sectional view along a line C-C ofFIG. 13A, showing the conductive material 18 after being patterned byetching.

In FIG. 15, the dashed line shows the position of the top surface of theconductive material 18 before etching the conductive material 18. Inother words, it suffices to perform etching by a thickness of S1 overthe inter-layer insulation film 16, as shown by the short arrow, whenetching the conductive material 18. However, for the part of the groove17, etching must be performed by a thickness of S2, which is thethickness of the inter-layer insulation film 16 plus the thickness ofthe conductive material 18 on the inter-layer insulation film 16, asshown by the long arrow. Accordingly, as shown in FIG. 15, etchingresidue R can be easily produced at the bottom of the groove 17.

A semiconductor device and a manufacturing method thereof for preventingthe problem of etching residue in the first embodiment are describedbelow as a second embodiment of the present invention.

Second Embodiment

FIGS. 16A, 16B, 17A and 17B show the structure of a semiconductor device200 according to the second embodiment. The semiconductor device 200according to the second embodiment is a DRAM. FIGS. 16A, 16B, 17A and17B show the structure when the formation of its wiring patterns (bitlines) 28 w is completed. In FIGS. 16A, 16B, 17A and 17B, the componentssame as the first embodiment are labeled with identical numerals and thedescription thereof are abbreviated.

As shown in FIGS. 16A, 16B, 17A and 17B, the semiconductor device 200according to the second embodiment includes, a plurality of transistorshaving the gate electrodes 11 and the source regions and drain regions12; the cap insulation film 13; the first inter-layer insulation film14; and the first contact plugs (cell contact plugs) 15, which areformed on the semiconductor substrate 10.

A second inter-layer insulation film 26 is formed on the firstinter-layer insulation film 14. The thickness of the second inter-layerinsulation film 26 is about 20 to 40 nm, which is much thinner than thatof the first embodiment. A groove 27 linearly extending in the samedirection as the extending direction of the gate electrodes 11 andexposing the top surface of the first contact plugs 15 at a bottomthereof is formed on the second inter-layer insulation film 26. Thegroove 27 is tapered such that the width at the top is wider than thewidth at the bottom. The bottom width of the groove 27 is preferred tobe approximately about the same or wider than the width of the top ofthe first contact plugs 15.

Wiring patterns 28 w extend on the second inter-layer insulation film 26so as to traverse the groove 27. In the groove 27, a plurality of secondcontact plugs (bit contact plugs) 28 c are arranged spaced apart fromeach other with a predetermined interval, the second contact plugs 28 cbeing formed integrally with the wiring patterns 28 w. It is preferredthat the second inter-layer insulation film 26 is thinner than thethickness of the wiring patterns 28 w. With the second inter-layerinsulation film 26 being thin and the groove 27 being tapered, theconductive material for use in forming the wiring patterns 28 w and thesecond contact plugs 28 c can be suitably embedded in the groove 27. Thesecond contact plugs 28 c and wiring patterns 28 w are formed by theconductive material, where a W or W/WN film can be used, for example.

Because the groove 27 is very shallow in the second embodiment, it canbe said that apart 28 c of the wiring pattern 28 w is connected to thecell contact plug 15, without distinguishing the bit contact plug 28 cand the wiring pattern 28 w.

The manufacturing method of the semiconductor device 200 according tothe second embodiment is explained below.

FIGS. 18A to 25B are process diagrams for explaining the manufacturingmethod of semiconductor device 200 according to the second embodiment,where FIGS. 18A, 20A, 22A, and 24A are schematic plan views in eachprocess, FIGS. 19B, 21B, 23B, and 25B are schematic cross-sectionalviews taken along a line D-D in each of the plan views, FIGS. 19A, 21A,23A, and 25A are schematic cross-sectional views taken along a line E-Ein each of the plan views, and FIGS. 19B, 21B, 23B, and 25B areschematic cross-sectional views taken along a line F-F in each of theplan views.

FIGS. 18A, 18B, 19A and 19B show the processes following those of FIGS.3A, 3B, 4A and 4B in the first embodiment.

As shown in FIGS. 18A, 18B, 19A and 19B, the second inter-layerinsulation film 26 having a thickness of about 20 to 40 nm is formed onthe first inter-layer insulation film 14. Subsequently, a resist mask 29is formed on the second inter-layer insulation film 26. The resist mask29 is formed so as to have a groove-like opening 29op located over thecell contact plugs 15.

Subsequently, by patterning the second inter-layer insulation film 26using the resist mask 19, the groove 27 linearly extending in the samedirection as an extending direction of the gate electrodes 11 andexposing the top surface of the first contact plugs 15 at a bottomthereof is formed in the second inter-layer insulation film 26, as shownin FIGS. 20A, 20B, 21A and 21B. By controlling the etching conditionwhen patterning the second inter-layer insulation film 26, the groove 27is formed to be tapered, with the width at the top being wider than thewidth at the bottom. Such a tapered groove 27 can be formed by thefollowing method, for example. After etching the silicon dioxide filmworking as the second inter-layer insulation film 26 by plasma dryetching under a condition of C₄F₈/O₂/Ar=20/20/400 sccm, 5 Pa, RF13.56MHz, 1000 W, and exposing the top surface of the cell contact plug 15,the etching gas is changed to O₂/Ar=100/100 sccm and the groove isprocessed into a tapered shape using the sputtering effect on thesilicon dioxide film 26 while removing the resist mask 29.

As shown in FIGS. 22A, 22B, 23A and 23B, the conductive material 28 isformed in the groove 27 and on the second inter-layer insulation film26. A W/WN film having a thickness of 40/10 nm is formed as theconductive material 28. It is preferred that the second inter-layerinsulation film 26 is thinner than the thickness of the conductivematerial 28. Because the groove 27 is shallow and tapered, the W/WN filmcan be easily embedded in the groove 27, even if PVD (Physical VaporDeposition) is used, for example.

In order to form a mask layer 30 for processing the conductive material28, subsequently, a silicon nitride film 30 a, an α-C (amorphous carbon)film 30 b, and a silicon oxynitride film (SiON film) 30 c are formed,each with a thickness of 150, 250, and 50 nm, upon which a resist mask30 r is formed in a wiring pattern. After etching the SiON film 30 c bya known plasma etching method using the resist mask 30 r as a mask andremoving the resist mask 30 r, the gas is changed to that having O₂ asits major component and the α-C film 30 b is etched using the SiON film30 c as a mask. The gas is further changed to freon or the like, and thesilicon nitride film 30 a is etched using the α-C film 30 b as a mask.After having removed the α-C film 30 b, the W/WN film 28 isplasma-etched by gas having Cl₂ as its major component, using thesilicon nitride film 30 a as a mask, as shown in FIGS. 24A, 24B, 25A and25B. Because the groove 27 is tapered, the W/WN film 28 embedded in thegroove 27 can be easily etched. Thus, the conductive material 28 thathas been linear within the groove 27 is separated to form bit contactplugs 28 c, and simultaneously wiring patterns (bit lines) 28 w isformed. Because the bit lines 28 w and the bit contact plugs 28 c areformed in such a manner, they are integrally formed.

By removing the silicon nitride film 30 a working as the mask layer, thestructure shown in FIGS. 16A, 16B, 17A and 17B can be obtained.

According to the second embodiment, a similar effect as with the firstembodiment is obtained and generation of etching residue in the groove27 can be prevented because the depth of groove 27 is shallow (thethickness of the second inter-layer insulation film 26 is thin) andtapered, facilitating etching within the groove 27 when patterning theconductive material 28.

It is apparent that the present invention is not limited to the aboveembodiments, but may be modified and changed without departing from thescope and spirit of the invention.

Although an example is described in the first embodiment that uses thesilicon nitride film 20 as a mask layer for etching the conductivematerial 18, and an example is described in the second embodiment usinga laminated film of the silicon nitride film 30 a, α-C film 30 b, andsilicon oxynitride film 30 c as the mask layer 30 for etching theconductive material 28, it is also possible that the laminated film usedin the second embodiment, or other types of masks are used in the firstembodiment as the mask layer. It is preferred to suitably select thematerial of the mask layer according to the patterning condition or thelike.

Although an example is shown using PVD to form the W/WN film working asthe conductive material 28 in the second embodiment, the invention isnot limited thereto and obviously other film forming methods such as CVDcan also be used.

1. A method comprising: forming a plurality of conductive regions substantially in line in a first direction; covering the conductive regions with an insulating layer; selectively removing the insulating layer to form an opening therein, the opening being elongated in the first direction to continuously expose respective parts of the conductive regions; depositing a conductive layer over the insulating film and in the opening, the conductive layer thereby including a projection correspondently to the opening, the projection including a plurality of contact portions each being in electrical contact with an associated one of the respective parts of the conductive regions; and patterning the conductive layer to form a plurality of interconnection lines separately from each other, each of the interconnection lines crossing the opening of the insulating layer and extending in a second direction that crosses the first direction, and each of the interconnection lines including an associated one of the contact portions of the projection.
 2. The method as claimed in claim 1, wherein the opening is formed with downwardly tapered so that each of the contact portions of the interconnection lines is downwardly tapered.
 3. The method as claimed in claim 1, wherein the forming the conductive regions comprises: forming an interlayer insulating film over a substrate; forming a plurality of contact holes in the interlayer insulating film; and forming a plurality of contact plugs in the contact holes, respectively, the contact plugs serving as the conductive regions.
 4. The method as claimed in claim 1, wherein each of the contact portions is substantially defined in the first direction by a width of an associated one of the interconnection lines and in the second direction by a width of the opening.
 5. The method as claimed in claim 1, wherein the second direction is substantially perpendicular to the first direction.
 6. The method as claimed in claim 1, wherein the forming the plurality of conductive regions comprises: forming a plurality of diffusion regions in a semiconductor substrate, the diffusion regions being substantially in line in the first direction; forming an interlayer insulating film over the semiconductor substrate including the diffusion regions; forming a plurality of contact holes in the interlayer insulating film, each of the contact holes exposing at least a part of an associated one of the diffusion regions; and forming a plurality of contact plugs in the contact holes, respectively, each of the contact plugs serving as an associated one of the conductive regions and being in contact with the part of an associated one of the diffusion regions through an associated one of the contact holes.
 7. A method comprising: forming a plurality of transistors, each of the transistors including a diffusion region, the transistor being disposed such that diffusion regions thereof are arranged substantially in line in a first direction; covering the transistors with an insulating layer; selectively removing the insulating layer to form a trench therein, the trench extending in the first direction so that respective parts of the diffusion regions of the transistors are included in the trench; forming continuously a conductive layer over the insulating layer and in the trench, the conductive layer comprising a first portion over the insulating layer and a second portion in the trench; and patterning the conductive layer to divide the first portion into a plurality of interconnection lines and the second portion into a plurality of plug portions at one time, each of the plug portions being electrically connected to an associated one of the diffusion regions of the transistors, and each of the interconnection lines being elongated from an associated one of the plug portions and running over the insulating layer in a second direction crossing the first direction.
 8. The method as claimed in claim 7, wherein the covering the transistors with the insulating layer comprises: forming an interlayer insulating film over the transistors; forming a plurality of contact plugs in the interlayer insulating film, each of the contact plugs being in electrical contact with an associated one of the diffusion regions of the transistors; and forming the insulating layer over the interlayer insulating mm having the contact plugs.
 9. The method as claimed in claim 8, wherein the trench is formed to expose at least a part of the contact plugs, and each of the plug portions being in contact with an associated one of the part of the contact plugs.
 10. The method as claimed in claim 7, wherein the trench is formed in a downwardly tapered shape so that each of the plug portions is downwardly tapered.
 11. The method as claimed in claim 7, wherein each of the transistors serves as a memory cell transistor and each of the interconnection lines serves as bit line.
 12. A method comprising: forming a plurality of word lines in substantially parallel to each other; forming a plurality of memory cell transistors each including a part of an associated one of the word lines as a gate thereof, each of the memory cell transistors including a first diffusion region to which a bit line is connected; the memory cell transistors being divided into a plurality of groups, the first diffusion regions of the memory cell transistors that belong to an identical one of the groups being arranged substantially in line in a first direction; forming an insulating layer over the word lines and the memory cell transistors; forming a plurality of trenches in the insulating layer, each of the trenches being in a line shape and extending in the first direction to position over the first diffusion regions of the memory cell transistors of an associated one of the groups; forming a conductive layer over the insulating layer and in the trenches, the conductive layer including a plurality of projections, each of the projections being in a line shape and extending in the first direction corresponding to an associated one of the trenches; and patterning the conductive layer to form a plurality of bit lines and to divide each of the projections into a plurality of bit contact plugs at one time, each of the bit lines extending in a second direction that crosses the first direction and including associated ones of the bit contact plugs, each of the bit lines being electrically connected through the associated ones of the bit contact plugs to the first diffusion regions of the memory cell transistors that belong to different ones of the groups.
 13. The method as claimed in claim 12, wherein each of the memory cell transistors includes a second diffusion region, and the method further comprises covering the bit lines with a first interlayer insulating film and forming a plurality of capacitors over the first interlayer insulating film, each of the capacitors being electrically connected to an associated one of the second diffusion regions of the memory cell transistors.
 14. The method as claimed in claim 12, wherein the forming the insulating layer over the word lines and the memory cell transistors comprises: covering the word lines and the memory cell transistors with a second interlayer insulating film; forming a plurality of plugs in the second interlayer insulating layer, each of the plugs being in electrical contact with an associated one of the first diffusion regions of the transistors; and forming the insulating layer over the first interlayer insulating film having the plugs.
 15. The method as claimed in claim 13, wherein the forming the insulating layer over the word lines and the memory cell transistors comprises: covering the word lines and the memory cell transistors with a second interlayer insulating film; forming a plurality of first plugs and a plurality of second plugs in the second interlayer insulating film, each of the first plugs being in electrical contact with an associated one of the first diffusion regions of the transistors, each of the second plugs being in electrical contact with an associated one of the second diffusion regions; and forming the insulating layer over the first interlayer insulating film having the first and second plugs.
 16. The method as claimed in claim 12, wherein each of the trenches is downwardly tapered to downwardly taper each of the bit contact plugs. 